On 1/25 I had a itter of pet-type mice born. One out of the seven is now having a bizarre coat malfunction. The baby in question is the solid gray (merle) at the top. In this first pic you can see she had a normal rex/texel coat.

A week or so later she suddenly lost all the fur on the back of her neck. I thought perhaps she had some sort of fungal or parasitic infection so I removed the entire litter from my mouse room until the babies were old enough to treat medically. There was no scratching or other symptoms in this mouse (Bainbridge) and no hair loss in her mother or littermates.

Then the fur on her body became sparse and coarse, but retained it's length, looking just like the coats on my lgh fuzzies. The hair on her face became noticeably shorter, even the whiskers, but kept its original thickness and texture.

Also at this time her merle markings came in.

Bainbridge, the doe in the pics, has a first cousin/half-brother named Howard who had a different sort of coat malfunction. When Howard first grew fur, he appeared to be a straight forward fuzzy, but before his coat came in completely it fell out everywhere but his nose, feet and tail. He was also *very* tiny. Here's what he looked like as a weanling (that's him with a normal pup half his age for comparison):

Around 7 weeks Howard suddenly hit a growth spurt and grew a coat that looks like a lgh fuzzy. Like Bainbridge, he is also merle. He now looks like this:

So, does anybody have any idea about what's causing this hair loss/change in texture? Is it coincidence that wonky (but somewhat different) fur problems showed up in the same line or does this indicate something genetic going on?

The fuzzy is normal, it happens, some lines are worse than others, but they can go through many coat phases. I've had some that changed coat densities, texture and length with every molt. It's something you have to select against if you want to breed consistant fuzzy's.

The Texel... I've seen that, and had that happen in my texels before. It's usually an animal who's parents, and grandparents were all Texel, usually it's a homozygous Rex. If you breed Texel together too much without breeding in a smooth coated mouse here and there the coat can become brittle and thin like that. Usually those mice grow out fairly normal by 12wks, but the coat will always be thin and it isn't something I would breed.

m137b: Thanks for your input! You are right about Bainbridge, it's quite likely that she is homozygous for rex and the vast majority of her ancestors are rex/texel. I wasn't aware that breeding so many generations of texel to one another could cause the coats to degenerate like this. I'm glad to have confirmation of her having a genetic quirk as there are several people interested in adopting her brother and sisters and I was worried that folks would take take home pretty babies only to have them turn into shock-haired freaks later.

Mrs. Beach: On the off chance that your theory is correct, I will be installing surveillance cameras near my electrical outlets. While I enjoy these silly costs and will be keeping Howard and Bainbridge as pets, I don't need more little "Einsteins"

So Bainbridge is now showing the beginnings of a thick even rex coat on her entire body...

m137b: What do you think about breeding her to a standard coated mouse? I really didn't intend for texel to get mixed up in my merle line. Bainbridge has the best merle markings of any mouse I've bred so far (of course I realize that the merle markings are not that heritable but it seems to me a well-marked mouse should have at least a slightly better chance of producing good marks than a poorly marked one). If I breed the texel out, will it have mattered that she had this crappy coat?